[erlang-questions] Mnesia and concurrency
Fri Dec 22 20:02:40 CET 2006
So does that mean that ets is a loophole of sorts around the
no-shared-memory rule that affects regular processes?
On 12/22/06, Serge Aleynikov <serge@REDACTED> wrote:
> That is only if all reads are serialized through a server process. As
> Hekan indicated, Mnesia (or ets) reads are not (e.g. look at
> mnesia:dirty_read/2, mnesia_lib:db_get/2).
> Yariv Sadan wrote:
> > How could one implement such a thing in Erlang? Assuming a table is
> > owned by a single process, and that process can only accept one
> > message at a time, how can multiple processes perform simultaneous
> > reads on the table?
> > Yariv
> >> No, the same goes for Erlang and Mnesia. The difference
> >> against other systems is that in Erlang we do not need
> >> separate OS threads to achieve this. It suffices to use
> >> separate Erlang processes (which may be hosted by any
> >> connected Erlang node). Any number of Erlang processes
> >> may read the same record without causing a locking
> >> conflict. But if one Erlang process is grabbing a write
> >> lock, it will get an exlusive lock for that record. The
> >> same principle is also valid for table locks.
> >> /Hеkan
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> Serge Aleynikov
> Routing R&D, IDT Telecom
> Tel: +1 (973) 438-3436
> Fax: +1 (973) 438-1464
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